It was a violation of Pakistani criminal law and prevented a medical conclusion about what killed the former prime minister, said Athar Minallah, who serves on the board that manages Rawalpindi General Hospital.

However, the police chief involved, Aziz Saud, told CNN that he suggested an autopsy be done, but that Bhutto's husband objected.

The revelation came on Monday after new videotape of Bhutto's assassination emerged, showing her slumping just after gunshots rang out.

The tape provided the clearest view yet of the attack and appeared to show that Bhutto was shot. That would contradict the Pakistan government's account.Read Bhutto's full medical report

A previously released videotape showed a man at the right of her vehicle raising a gun, pointing it toward Bhutto, who was standing in her car with her upper body through the sunroof. He fired three shots, then there was an explosion.

In the video that emerged on Sunday, Bhutto was standing, and her hair and scarf appeared to move, perhaps from the bullet. Bhutto fell into the car, then came the blast. Watch new tape showing apparent gunman »

These images seem to support the theory that Bhutto died at the hands of a shooter before a bomb was detonated, killing another 23 people.

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Doctors at Rawalpindi General Hospital declared the 54-year-old dead hours after Thursday's attack, but the cause of her death has been widely debated.

Pakistan's Interior Ministry announced on Friday that Bhutto died from a skull fracture suffered when she fell or ducked into the car as a result of the shots or the explosion and crashed her head onto a sunroof latch. See the likely sequence of events »

Bhutto's family and political party maintain that the government is lying, and insist she died from gunshot wounds.

Bhutto's husband, in an interview with CNN's Wolf Blitzer on Monday, called for an international investigation into his wife's death, saying the new video proves the Pakistani government "has been trying to muddy the water from the first day."

Zardari also called on the U.S. government to push for an international probe.

"I want them to help me find out who killed my wife, the mother of my children," he said of the Bush administration.

Javed Iqbal Cheema, spokesman for Pakistan's Interior Ministry, said the government's conclusion on Bhutto's death was based on "absolute facts, nothing but the facts" and "it was corroborated by the doctor's report."

But Minallah issued an open letter on Monday and released the doctors' clinical notes to distance them from the government statement, and he also talked to CNN.

In the letter, Minallah said the doctors "suggested to the officials to perform an autopsy," but that Saud "did not agree." He noted that under the law, police investigators have "exclusive responsibility" in deciding to have an autopsy.

Minallah told CNN that he was speaking out because the doctors at the hospital were "threatened."

"They are government servants who cannot speak; I am not," he said. He did not elaborate on the threats against the doctors.

He said the lack of an autopsy has created "a perception that there is some kind of cover-up, though I might not believe in that theory."

"There is a state within the state, and that state within the state does not want itself to be held accountable," Minallah said.

Cheema said the government had no objection to Bhutto's body being exhumed for an autopsy if the family requested it.

Her widower has said the family was against exhumation because it did not trust the government.

Minallah said the family could not have prevented an autopsy at the hospital without getting an order from a judge.

The three-page medical report, which was signed by seven doctors, described Bhutto's head wound, but it did not conclude what caused it. It noted that X-ray images were made after she was declared dead.

The wound was described as an irregular oval of about 5 centimeters by 3 centimeters above her right ear.

"Sharp bones edges were felt in the wound," it read. "No foreign body was felt in the wound."E-mail to a friend